El Nino, La Nina, and.... La Nada????

Odds are you've heard of El Nino and La Nina (the abnormal warming and cooling of the eastern equatorial Pacific waters, respectively), especially if you've been reading my blog.  This past winter, the Pacific Ocean was in a very strong La Nina, which helped to produce the heavy snows and cold winter across the U.S., along with the severe drought conditions over the southern U.S. this year.

Late last winter, the strong La Nina that helped to ravage the nation early last winter finally came to an end and the Equatorial Pacific waters returned to their normal temperatures.  But this presents it's own issues.  Usually, when a La Nina period ends, an El Nino period begins, even if it's just a weak one, and vise versa.  So the waters off the coast of western South America never stay normal for very long.  But this year, we are seeing an unusually long period of near normal water temperatures.  In fact, one scientist, Bill Patzert, a climatologist and oceanographer at NASA's Jet Propulsion Laboratory has coined the term "La Nada" to describe this period of normalcy.

The latest satellite data of Pacific Ocean sea surface heights from the NASA/European Ocean Surface Topography Mission/Jason-2 satellite show near-normal conditions in the equatorial Pacific. The image is based on the average of 10 days of data centered on June 18, 2011. Higher (warmer) than normal sea surface heights are indicated by yellows and reds, while lower (cooler) than normal sea surface heights are depicted in blues and purples. Green indicates near-normal conditions. (Credit: NASA/JPL Ocean Surface Topography Team)

The problem lies in climate forecasting.  A "La Nada" period brings with it a large amount of uncertainty in the forecasts.  Many scientists believe that a "La Nada" period will bring about "normal" weather conditions, however, previous similar "La Nada" periods have delivered unruly jet streams and wild weather swings, going from one extreme to the next.  And we actually saw this!  As the La Nina ended and "La Nada" began, the jet stream was able to swing back and forth across the U.S. wildly and helped to bring the blizzards to the Midwest, South, and Northeast, along with the tornadic storms across the South and Tornado Alley. 

However, some climatologists are wondering if another warm El Nino pattern will soon emerge - which would be great timing for the United States!  If an El Nino pattern were to develop this summer, much needed rains would likely come to the drought and wildfire stricken southern U.S.  Plus, a late summer El Nino pattern also dampens the hurricane season in the Atlantic, which peaks in late August & September.  Thus, it would bring much needed rain to the South along with a mild hurricane season!

Climatologist and Oceanographers will continue to monitor the progress of the "La Nada" and watch for signs of an emerging El Nino or a returning La Nina.  Until then, try to enjoy your summer!

2010 - 2011 Winter Outlook

Here in the Upper Midwest, we are use to the cold and snowy months of winter.  However, some years are colder and snowier than others if a La Nina is in effect.  La Nina is associated with cooler than normal water temperatures in the Equatorial Pacific Ocean, the exact opposite of an El Nino.  Both La Nina and El Nino have dramatic impacts on our weather here at home, and around the globe!  For example, last year's El Nino resulted in record-breaking rain and snowfall causing severe flooding in parts of the U.S. while other areas of the nation saw record heat and drought.  Even though La Nina is the opposite of an El Nino, it too can bring weather extremes to parts of the U.S.

The Climate Prediction Center (CPC) has recently come out with a news report saying that not only is a La Nina in place, but it will strengthen and persist through the winter months of 2010 and 2011.  So what does this mean for the winter around the U.S.?

Here are some regional highlights:

The Pacific Northwest

Expect to see a colder and wetter than normal winter.  La Nina typically brings cooler than normal and snowier conditions to this region during the winter months.

The Southwest

Don't be expecting to see much snow here.  All of the southern states typically see a warmer and drier winter during a La Nina, which also increases the risks of wildfires in these regions.

Northern Plains
Expect plenty of snow!  La Nina typically brings colder and wetter conditions to this area of the nation during the winter months.  This will also lead to a higher likelihood of flooding during the spring melting season!

Southern Plains, Gulf Coast, & Southeast
These areas are already experiencing some very dry conditions with some areas facing severe drought conditions!  Unfortunately, like the southwest U.S., La Nina also brings warmer and drier conditions during the winter months to this area as well, which will only help to prolong the drought conditions here.

Florida
Drier than normal, but has equal chances of above or below normal temperatures.  This will also create above normal wildfire conditions here.

Ohio & Tennessee Valleys
Expect more storms this winter as La Nina typically brings wetter, but warmer, conditions to this area during the winter months.  The above normal precipitation will also likely lead to a higher likelihood of flooding in the area.

Northeast & Mid-Atlantic
This is one area La Nina has very little direct impact!  Weather patterns here are more driven by conditions over the North Atlantic and the Arctic.  However, if there is enough moisture in place in the region, areas in the Northeast could see above normal snowfall.

Central U.S.
This area is right in between the very dry and warm portions of the southern U.S. and the cold and wet conditions of the northern plains that La Nina typically brings.  Thus this area is likely to see equal chances of above or below normal precipitation and temperatures during the winter months.

Hawaii
Headed to Hawaii on a winter vacation?  You might want to pack an umbrella.  La Nina typically brings the island state wetter conditions from December through February.  However, the drought they have been seeing here this past year is expected to continue through the winter, with many areas on track to see their driest year ever!  Drought relief is most likely on the smaller islands in the chain.

Alaska
La Nina often brings a colder than normal winter to this frigid state, and this year should be no exception. 

Here at home in Wisconsin, I'm expecting to see a slightly cooler than normal winter with more snowfall, especially along the shores of Lake Superior in the north and the southeastern portions of the state.  Granted, this outlook does not project where and when snowstorms will hit or total seasonal snowfall accumulations, but it gives us a better view at to what to expect from mother nature during the coldest portion of our year.

Until next time,
Keep your eye on the sky!

Cold, Snowy Winter Ahead?

That's right.  With all this heat and humidity lately, I thought it would be a good time to give your brain a mental cool down with some chilly thoughts about this upcoming winter.  Anyone who has been watching weather-related news the past few months may have heard of our recent transition from an El Nino to a La Nina in the equatorial Pacific Ocean.  During a La Nina event, the surface waters of the equatorial Pacific are 0.5 degrees Celsius or greater below normal.  Both El Nino and La Nina effect global weather patterns, and La Nina tends to impact our weather the most during the winter months when the jet stream is the strongest over the United States.  Typically, La Nina winters in Wisconsin (especially during moderate to strong La Nina events) tend to be colder than normal and wetter/snowier than normal.  The current La Nina is forecasted to become moderate to strong over the next several months.

The National Weather Service in Milwaukee, WI has recently done a study comparing La Nina event years to the normal climatic observations for both Madison and Milwaukee in southern Wisconsin.  The study concluded that both cities say below normal temperatures between January and March AND more snowy/wetter conditions during the same time frame.  This finding is very similar for the rest of Wisconsin as well.  Thus, for this winter, you could expect more snow to fall across Wisconsin with slightly cooler conditions, especially from January to March when La Nina events tend to impact the Midwest the most.